The project is designed to investigate the mechanisms used by cells to assemble their various functionally distinct membrane systems from component lipids and proteins. The ciliated protozoan Tetrahymena pyriformis will be employed as a model system. Building on present knowledge of intracellular lipid mobility, future studies will emphasize 1) the assembly of proteins into membranes, 2) the mobility of structural lipids and proteins within membranes, 3) factors regulating the supply of components for membrane growth, and 4) changes in membrane properties resulting from the flux of structural components. Much of the experimentation will involve radioisotope labeling of lipids or proteins as a means of determining their intracellular deployment. Cell fractionation and electron microscope level radioautography will be used for locating labeled molecules. Membrane development in logarithmic phase cultures will be compared with that observed under a variety of other physiological conditions, such as the stationary growth phase, starvation, synchronous division, and induced endocytosis. In all aspects of the work, a strong effort will be made to correlate the metabolic interactions among the various membrane systems which together make up the whole cell.